In recent times, the use of asphalt-impregnated polyester sheet for roofing construction has been found to provide excellent results. The polyester sheeting is generally treated with asphalt and other water-resistant materials in the factory, because of the difficulties experienced with applying water-proofing materials to the polyester at the roof site.
Untreated, non-woven polyester sheet does not generally withstand heat, and does not easily absorb hot asphalt.
Untreated, polyester sheet has been used with asphalt in cold-process roofing systems, wherein the asphalt is modified with latex or polypropylene and sprayed in a cold liquid state upon the polyester sheet. The cold process roofing systems have not been entirely satisfactory, because they tend to remain tacky for many months. This tackiness hinders the completion, repair and/or inspection of the roof, since the roof cannot be walked upon while tacky.
Even where hot asphalt systems have been contemplated with the use of polyester sheet, the asphalt generally requires torching on the roof, which is an unsafe, fire-hazardous procedure.
Therefore, most roofing applications using polyester materials have been with a polyestermat, i.e., a factory asphalt-impregnated polyester sheet.
The drawback of using factory impregnated polyester sheeting, however, is the high cost and inconvenience of shipping and handling these heavy rolls of material.
The present invention contemplates the construction of a roof using a polyester-hot asphalt or coal tar process at the roofing site, without the aforementioned disadvantages.
Hot, built-up roofing can now use plain, non-woven polyester sheet for the reasons that the polyester is now being manufactured with a resin treatment that assists the polyester to withstand the temperature (450 degrees F) of hot asphalt and other hot-applied water-proofing ingredients.
In addition, torching the asphalt on the roof is no longer necessary with the advent of a new hot pumping system, wherein the asphalt is pumped in a hot fluid state to the roof.
The advantages of building-up a roof with hot water-proofing ingredients and polyester sheeting are many.
The rolls of plain, non-woven polyester sheet are light in weight and inexpensive to purchase and ship.
Plain polyester rolls are easier to work with, and a single, light-weight ply is often all that is required to produce an efficacious roof construction.
According to this invention, the polyester and asphalt layers can be melded together and simultaneously directly attached to the roof substrate as a composite membrane. This inventive method of forming and affixing a composite membrane simultaneously, in situ, not only reduces the costs of fabrication, but also provides a roof of better quality and adhesion.
The inventive method and construction will be explained in more detail, hereinafter.
The composite membrane technique of this invention can be used with different roof substrates and overlays of foam, such as polyurethane and isocyanurate, to provide a roof composite construction of exceptional durability.
Where roof substrates are comprised of seams, it has been found that asphalt will leak into the seams. An additional base sheet must be provided below the polyester sheet to maintain a given quantity of water-proofing ingredients to form the composite membrane, i.e. enough asphalt must be provided below the polyester sheet in order to rise through the polyester and meld with the asphalt placed above the polyester sheet. The base sheet is first adhered to the roof substrate using a thin layer of asphalt. The polyester and asphalt composite is then applied over the base sheet, as previously described in U.S. patent application Ser. No. 704,143; filed: Feb. 21, 1985.